This invention relates to magnetic recording media and more particularly to a thermoset polymer blend binder system for rigid magnetic storage media.
The increasing demands made on high performance magnetic recording media call for further improvements in the mechanical and electromagnetic properties of the recording media. As regards the mechanical properties of the media, the requirement to achieve long life and good service characteristics calls for increased tensile strength, superior abrasion resistance of the coating film and the ability to retain a liquid lubricant on the surface to reduce the head coefficient of friction during high speed recording. Improvement in electromagnetic properties require a binder system capable of dispersing magnetic particles uniformly with higher loading, coupled with the ability to provide acceptance of magnetic particle orientation in the desired direction under the influence of a magnetic field and to retain such particle orientation after curing the resin.
Orientation of the magnetic particles by the action of a magnetic field on the coating before it is dried improves the performance characteristics of the finished recording media by increasing the signal output and reducing the background noise level.
It is further necessary that the rigid magnetic coating binder system have the ability to produce a thinner coating, since the magnetic resolution is enhanced as the coating is made thinner.
All of these requirements: high tensile strength, superior wear resistance, high lub acceptance, low head friction, low head stiction, low lube spin-off, high magnetic particle orientation with high particle loading, uniform dispersion and thin as coated film thickness; require a unique polymer binder system. Presently available coating systems are unable to satisfy these conditions.
U.S. Pat. Nos. 4,268,556 and 4,156,052 disclose the importance of lubricant application to the rigid magnetic recording media to reduce head friction and wear. Various lubricants and methods are selected for this application. None of these prior art patents show or teach the microcellular structure in the base binder system to achieve these requirements. The use of polymer resin additives to improve the abrasion resistance of a magnetic coating is disclosed in U.S. Pat. No. 4,304,806 and the use of non-magnetic wear particles for such purpose is shown in U.S. Pat. No. 3,843,404. The present invention applies a thermoset polymer blend technique to produce a superior abrasion resistance film surface that pervades the entire macroscopic region rather than discrete areas.
Numerous publications show various dispersant combinations for magnetic recording coatings, including U.S. Pat. No. 4,049,566. The binders of this invention have their own dispersion power without the addition of dispersing agents.
Unlike the prior art, the present invention discloses a dual thermoset polymer system that results from a blending of two optimum thermoset polymer networks, processed in such a way that by physical entanglement rather than through chemical bonding, the final properties of the magnetic coating meets all desired requirements for a high performance, rigid magnetic recording media.